Re: GPSD does not see Galileo

[Gary E. Miller]

Yo David!

On Fri, 22 Jan 2021 15:25:05 +0000
David Taylor <gm8arv@yahoo.co.uk> wrote:

> The SNR on this particular Raspberry Pi and antenna is 15 dB - not
> very high:

Not high?  That is barely high enough to read the data channel.
A receiver would noly use 15dB signals as a last resort.

>    https://www.satsignal.eu/mrtg/performance_raspi-25.php

I do not see individual SNR there, only average.  Your average is also
bad.  Older GPS would never work a less than 30dB.  You are lucky to
get much of anything.

> I'm using (IIRC) the Visible and Used values from gpsd.  If I was
> doing this again I might use fewer GLONASS and more Galileo channels.

Hardly matters, you need a much better antenna and/or skyview.

For best timing, you only use one constellation.  GPS is best for that,
but some think Galileo may get better, if they stop losing the keys.

> This isn't for precision timing, and getting some lock is
> satisfactory here.  I'm measuring RTC performance to within a
> millisecond and getting something which looks sensible.  Setting the
> RTC to noselect just gets an offset value of zero, which isn't
> useful.

Hmm, I remember that working.  Guess not.  Old age.  The other trick is
to give it a large offset (1 sec) so that ntpd never locks on to it.

RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        gem@rellim.com  Tel:+1 541 382 8588

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    "If you can't measure it, you can't improve it." - Lord Kelvin

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